1. Field of the Invention
The present invention generally relates to a press machine and, more particularly, to a metallic die device for a press machine, which is applied to a press machine that can bend not only the one side but the two sides of a workpiece (hereinafter referred to as "work") simultaneously, and which can correctly press a portion of the work with the same die at an arbitrary bending angle and can press the work at high precision by preventing escape and deformation of a lower metallic die; and a metallic die device for a press machine, which is applied to a press machine for bending a work, and which can bend the work in an arbitrary size and at an arbitrary angle without changing the metallic die, thereby easily pressing the work to have a box shape, and so on,
2. Description of the Related Art
A recent press machine must cope with many requirements, e.g., small quantity with many items, flexibility, and high precision.
For this purpose, a press machine employing a control technique based on a computer program, i.e., a press machine using an NC device has been used in practice.
Generally, in a press machine of this type using an NC (Numerical Control) device, a work is conveyed to a pressing position and positioned there in accordance with a command from the NC device. Then, a hammer is operated by a command from the NC device to move a punch as an upper metallic die downward, and press the work present between the upper metallic die and a die serving as a lower metallic die.
Conventionally, however, when a work is to be pressed by, e.g., bending by a press machine of this type, the size of the bending width or the bending angle for bending press is changed. The bending precision corresponding to the thickness or material of the work is changed. In this manner, the press machine is stopped each time, a suitable die is selected from a large number of metallic dies, and die exchange and size adjustment are manually performed. Such a press technique has a very poor productivity and is very uneconomical since manual exchange occupies a large part of the entire press time and a large number of different dies are required because the die exchange requires several tens of minutes. In this manner, in the conventional press method, when the size of the bending width and the thickness or material are changed, fine adjustment of the size cannot be automatically performed.
The assignee of the present application solves the above drawbacks by a press machine disclosed in Published Examined Japanese Patent Application No. 1-37214.
More specifically, according to this press machine, each of the upper and lower metallic dies comprises a pair of dies. One lower metallic die is fixed, and the other lower metallic die and the two upper metallic dies are set to be movable to and away from the fixed lower metallic die. The upper and lower metallic dies are moved by a controllable driving unit. As a result, work holes can be formed at desired pitches, the size of the bending width can be freely set, and at least one upper metallic die can be moved to a desired position by a small distance.
Then, even when works having different thicknesses are to be pressed, the pressing portions on the two surfaces of each work, i.e., the two sides of each work as the pressing portions can be simultaneously bent at a right angle without exchanging the metallic dies, thereby increasing the press efficiency.
In the above press machine, however, since the upper metallic dies move downward toward the lower metallic dies, the two sides of the work as the pressing portions can be bent only at the same angle, i.e., the right angle.
Furthermore, in the conventional press machine described above, as shown in the partially enlarged view of FIG. 45A, when the force of a punch 102 is applied to a lower metallic die 19 of a movable die plate 13 during bending of a work W, the movable die plate 13 escapes through the lower metallic die 19, and one bent surface Wa of the work W cannot be bent at a preset angle (right angle in this case) or in a preset bending width.
In the conventional press machine, as shown in FIG. 45B, even when the position of the movable die plate 13 is stationarily held, since the load of the work W during bending is directly applied to a lower metallic die 18 and the lower metallic die 19, both the lower metallic dies 18 and 19 are deformed inwardly, and the bent surface Wa and a bent surface Wb of the work W cannot be bent at the preset angles or in the preset bending widths.
In this manner, in the conventional press machine, when each of the upper and lower metallic dies is constituted by divisional metallic dies for the purpose of simultaneously bending the two surfaces of a work, escape and deformation of the metallic dies arise, and the work W cannot be bent at high precision.
Furthermore, in conventional bending by the press machine as described above, regarding bending in a desired arbitrary size, only two surfaces of a work can be bent at only the right angle.
Since formation of a product by bending three or more surfaces cannot be performed, formation of a box by bending four surfaces, which is common as a product, and bending at an arbitrary angle other than the right angle cannot be performed.
When two opposing surfaces are to be bent at a short distance or are to be bent to have large heights, the metallic dies need to have a small thickness and a large height. Then, when the metallic dies are pushed by a horizontal force generated during work press, the metallic dies escape, or the metallic dies themselves are bent or deformed, and the work cannot be bent at an accurate angle or in an accurate size on the order of several tens of microns.
Furthermore, when works are to be pressed to have different materials, thicknesses, and bending shapes, thus providing different products, since the variations in the bending angles caused by the variations in hardness and rigidity of the materials and errors in thicknesses are large, high-precision bending on the order of several tens of microns cannot be performed.
More specifically, one of the background techniques requiring high precision as described above is so-called laminated sheet metal working.
Laminated sheet metal working is applied to working of a chassis of an amplifier used in, e.g., a satellite communication system that requires high-quality, stable communication free from wave leakage. Conventionally, a chassis of this type is formed by die casting and cutting. However, die casting and cutting cannot cope with the many requirements described above in the Field of the Invention.
For this reason, according to an application field of laminated sheet metal working, several thin plate chassis components each pressed into a box or the like in advance by a turret punch press are adhered by spot welding or the like to fabricate a thick target chassis. More specifically, this laminated sheet metal working requires high precision on the order of several tens of microns as described above in order to fabricate, e.g., a thick chassis free from electric wave leakage by laminating (fitting) several thin sheet metal works that are pressed in advance.